You really need to work on those animations. The most important advice I can give is to shift the model's center of gravity and torso whenever an action happens to give a sense of weight. Try moving the hips and adjusting along the spine with each action, and turning the torso in time with any extensions of the arms. And keep practicing!

I love the model itself though, and congrats on actually making infantry, something most mods never bother with.

Human motion is one of the hardest things to perfect in animation. It's not easy, nor is it easy to really figure out how we move beyond how we think we move. The engineer in its current state is a perfect example of how we think we move instead of how we actually move.

Human motion is never in lines: always arcs or circles
Human motion is full of overlapping actions and actions that have to happen to maintain our balance (the positioning of the belt/shoulder line when we walk like Sketch mentioned)
Human motion always has some causation because we have to get power for each action. An example would be before we jump, we crouch and lean in the opposite direction (anticipating action)
These are just a few of a collection called the Principles of Animation, and there are plenty of examples out on the web to help you understand and integrate each principle.

The essence of human life is that it's a pattern and randomness all together. There's distinct timing, but it varies. Best thing I can suggest is video take yourself, and really dissect the motion. I would also look up drawn out walk cycles and breakdowns of 2D animation, especially Disney..they are the masters at creating lifelike motion.

Not a bad lookin engineer :D
I'm not as confident about the speech, maybe things like "I can fix anything", "thats not a problem", "an engineer's work is never done", "I can repair that easy", maybe more stuff like that.